Health information technology (IT), particularly in the form of electronic medical records (EMRs), is increasingly recognized as an important tool for improving patient safety and quality of care. Despite the potential of EMRs to improve the health of individuals and the performance of providers, many healthcare organizations have not been able to realize the intended benefits of EMR systems because of failed implementation efforts. Theory and practice suggest that social influence may play a critical role in enabling - or hindering - the implementation process. However, there is a paucity of research that examines who is influential and how healthcare practitioners influence one another's use of new technology. In response to this pressing gap in the literature, the objective of this study is to examine the role of opinion leaders - individuals perceived as having particular influence on the beliefs and actions of their colleagues - during the implementation of an EMR system. Using a mixed methods approach that leverages both quantitative (i.e., surveys) and qualitative (i.e., interviews and observations) methods, the proposed work entails collecting primary data for six clinical units in one large academic hospital over a one year time-span. Using survey data collected at three time points (six months pre-implementation, one month post-implementation, six months post-implementation), the first aim of the study is to identify opinion leaders and to assess individual-level predictors of who is perceived to be an opinion leader over the course of the implementation process. Using the same survey data, the second aim of the study is to estimate the extent to which opinion leaders influence their colleagues' perceptions and use of the EMR system. The third aim of the study is to use interviews and observations to identify specific behaviors and strategies that opinion leaders use to generate support or resistance for implementation efforts. The findings from this work will advance understanding of the role of social influence in EMR implementation and provide insight into how to leverage highly influential individuals to convince others to embrace EMRs, and ultimately, to use EMRs more effectively.